1. Field of the Invention
The present invention relates generally to an apparatus for holding a heat exchanger core during a manufacturing operation.
2. Background Information
Typical heat exchanger cores are manufactured by assembling a plurality of tubes interleaved with fins between a pair of side support members. The core is precompressed by a variety of known methods prior to brazing to maintain the tube and fins in proper relationship. One known method is to precompress the core with one or more steel bands completely surrounding the core before brazing. After banding, the core is inserted into a furnace and heated until it brazes together. After brazing, the steel bands are cut from the core and discarded, resulting in a large amount of waste. In addition, these bands often distort and/or skew the core which can result in leaks and/or improper vehicle fit.
Other types of brazing fixtures have been proposed such as that shown in U.S. Pat. No. 5,165,163, assigned to the assignee of the present invention and which is shown in FIG. 1. The brazing fixture 10 includes a plurality of brazing stations 12 each having a pivotal lever 14 which applies a compressive force against one of the side support members 16 of the heat exchanger 18 while the other side support member 20 is held stationary in the fixture 10. The fixtures 10 typically hold up to six heat exchangers. However, these fixtures tend to become corroded in the brazing atmosphere, reducing the effectiveness of the compressive force applied against the core. Also, these fixtures usually are not used upstream of the braze process due to sheer weight and mass. Heating these fixtures in a braze furnace requires much energy due to their large mass. This adds expense and delay to the manufacturing process.
A third type of brazing fixturing is proposed in U.S. Pat. No. 3,894,580. In this fixture, a pair of generally parallel ties extend between each of the side support members to fix the core in a predetermined position prior to the brazing operation. The disadvantages of using the generally parallel ties is that unless an elaborate and complicated clamping mechanism, such as shown in U.S. Pat. No. 3,894,580 is utilized on each end of the ties, the heat exchanger core can still skew as a result of normal process handling and/or shrinkage and thermal cycling during the brazing operation. This skewing or misalignment of the heat exchanger core often results in deleterious effects upon the core such as leaking and/or improper vehicle fit.
U.S. Pat. No. 5,450,997, also assigned to the assignee of the present invention, overcomes the problems associated with some prior art brazing fixtures by providing a pair of rod members which engage the side support members of the heat exchanger. The rod members are diagonally placed in an overlapping crosswise relationship to prevent skewing. However, these rod members require locating holes be formed in the side support members which is not always possible.
It would, therefore, be advantageous to provide an effective, simple fixturing apparatus which can easily be used during the fabrication, processing, and brazing of the heat exchanger core to prevent the skewing or misalignment of the heat exchanger core and which minimizes the amount of heat energy required.
It is an object of the present invention to provide a brazing apparatus which applies a constant compressive force during the brazing process in a much more cost effective and less complicated structure.